Communication system



Patented Oct. 23, 1945 UNITED STATES PATENT OFFICE.

COMMUNICATION SYSTEM Werner llasenberg; Rio de Janeiro, Brazil J 1 Application May 17, 1944, Serial No. 535,996

(01. ire-1) 5 Claims. The present invention relates to communication systemsand more particularly to intercommunieating systems of the loudspeakingtype compris-i ing a large number of stations each equipped with a speaker unit which serves alsoas transmitting means and wherein two-way conversationmay be established between any of two stations;

Loudspeaking communication systems are known to the art built up by so called master sta-. tions each comprising a dynamic speaker of the moving coil type, suitable amplifier means, a

communication direction control switch and switch means for selecting the lines for trans' mitting to. a selected station. Formaster stations of this type, generally n+1 interstation con-' ductors: or channels must be provided for "each station, i. 6.1 one :for receiving. from and n for transmittingto other stations, thereby being equal to. the number of stations with which it is.

desired to communicate. Considering also the fact that it happens very seldom that all the stations provided in such system are being in the number of stations operated by only a few number of amplifiers sumcient to correspond the requirementsva'ccordingly to the average of daily communication tobe effected. This is attained by combinations and arrangements similar to the telephonicP. B. X system, locating a'group of amplifiersat a central ofiice and connecting each to a switchboard circuit at the central-office. 1

A more specific object is to providemeans permitting the direction of communication to be controlled by the remote stations. This is attained by a particular arrangement of acommunication control unit which combines the amplifier; the

reversing. switch and control circuit means 'to an exchangeable communication circuit element adapted to be inserted between the calling and theicalled stationscommunicaton channls' Another object is'the simultaneous use of the proper communication. channels forboth transmitting and controlling as well as for conveying signals to the operator, at the central-office. While those arrangements and combinations are conventional'to the prior art and partly utilized in telephonic-circuits; the specific arrangement described later on in'detailis noveland char-ac} terls'tic of th'e present invention;

Further objects and advantages of the present invention will become apparent from the insuing description in the course of which reference is had to the accompanying drawing in which:

Figure 1 is a schematic diagram illustrating the entire communication circuit between two remote stations including the communication control unit. t

Figure 2 shows a schematic diagram of a P. B. X system of loudspeaking intercommunication in which the invention is embodied.

Referring first to Figurel, the reference numerals l and 2 designate two stations of equal construction and circuit, each having a speaker unit 3 and 4 respectively, input terminal 15 and 6 respectively and the push-to-makeswitch I and 8 respectively. It is further provided in the stations single terminals 9 and i0 and transformers l l and I2, the latter being with one winding-the line side windingconnected across the input terminals 5 and 6 respectively. The other windstation bymeans of its communication channel ductors 28 and 29 to conductor the source of voltage 20.

ing of transformers II and 12 leads to the moving coil of the speaker unit. The line side winding of transformers II and I2 have a centertap which is connected to the single terminal 9 and [0 respectively by means of conductor [3 and I4 ineluding switch 1 and 8 respectively.

The circuit arrangement enclosed'within rectangular I5 represents what I desire to call the communication control unit, containingan amplifier [6, a communication direction control or reversing' switch ll, an electromagnetic device l8, signaling device H! which may be a lamp or the like, a source of voltage 20, inlet and outlet 2| and 22 respectively,v a ground terminal 23 and two transformers 24 and 25.

Dealing now with the inner circuit of the communication control unit [5, it will be seen that the inlet and outlet transformers 24 and 25 respectively are with their line side winding connected across the inlet and outlet terminals 2| and 22 respectively. The line side windings of these transformers are centertapped, the centertap of the line side winding of transformer 24 being connected over conductor 26 to the electromagnetic devicelB, whereas the centertap of transformer winding 25 leads over conductor 21 to lamp IS. The other ends of lamp [9 and electromagnetic device 18 are conneetedby con 30 which leads to The input and outputterminals 3'! and 32 of amplifier l6 have one of their terminals con'-' nected to a common or bus wire 33 which leads to ground terminal 23. Also the source of voltage 20 and the primary windings of transformer 24 and 25 have one of their ends connected to the common conductor 33 by conductors 34, 35 and 36 respectively.

The other ends of the primary windings of transformers 24 and 25 and the ungrounded terminals of input and output of amplifier I6 are connected to the reversing switch I! by means of conductors 31, 38, 39 and 40 respectively.

As it is shown in Figure l the communication control unit I is connected to the stations l and2 by communication channels 4| and 42, the first outgoing from inlet terminals 2| leading to input terminals 5 and the second interconnecting the outlet terminals 22 of the control unit with the input terminals 6 of station 2. l a

The reversing switch H, in order to control its position, is combined with and operated'bythe electromagnetic device I8. The communication direction control switch I! is shown in its'nor'mal position which is defined by the fact "that the output of amplifier 16 leads to the inlet 'transformer 2 4 and theinput tothe outlet transformer 25.

Dealing now with tthe'operation of the sy'stem shown in Figure 1 it is supposed that the party at station I is listening to the-speech transmitted by the party at the station 2, it will be seen that the voice induced currents travel from terminal 6 of "station 2, overcommunication channel 42 to the communication control unit reaching thereat their outlet terminals 22. The voice induced currents are conveyed farther on over transformer 25, conducto 38, direction control switch I1, and conductor 39 to the input 3| :o'f amplifier I6. The-amplified sound currents leave theoutput 32 and travel over conductor "40,:di-rection control switch |'I, conductor 31 to transformer 24, leaving the communication control unit I5 at inlet terminals 2|;en'terin'g communication channel 4| and go on up to input terminalsfi of-station I. 7

With the intention to transmit in the "opposite direction, which happens when communication direction control-switch I1 is -reversedto its secend position, all what the party-atistation I to do, is closing' the switch 'I provided at the station. .By doing so, acontrol circui-t is completed, thereby operating the electromagnetic -devic'e I-B embodied in the control unit I5. The normally open and now closed control circuit is built upin the following manner: Outgoing from ground terminal 23 of the unit 1 5 over common conductor -33, and-conductors 34 and 3|]- inoludihg the battery 20, a control current 'flows over "conductor 29 thru the electromagnetic device 1 8 and reaches over conductor 26 the ce'ntertap of the line side winding of transformer 24 and from there travelling fa'rther On to the I inlet terminals 2| leaving the unit I5 and is carried on by 'co'mmunieation channel 4| up to station 1 where it enters the line side windingof transformer I, and going on over centertap of the latter to terminal 9 of'the station. 'The circuit is completed by the ground I connections of st'a'tion and control unit; The arrangemen't' now described enables the party at stationl to control the "communication solely by operating the push-to-make'switch I, as well as to use theproper communication channel M for simultaneouslycarrying .on both sound and control currents. I

The signal circuit embodied inx'the systemsof Figure 1, like the 'controlcircuitisnormally open. When the party at station 2 desires "to emit ra -signal to the communication control unit (to attract the attention of the operator thereat, as it will be described later on) switch 8 at station 2 has to be closed, thu-s completing the signal circuit. When this is done the signalling device I9 at control unit I5 will be operated, for instance,

-at-station 2, centertap of the latter, conductor I4 including switch 8, terminal I0 and the completionby the ground connections of station 2 and control unit I5. The arrangements and combinations describedand illustrated in Figure 1, have given b'est results, and the communication effectedbetween two stations located at a distance of quite a mile has proved to be free of failures and disturbances or other difficulties.

The embodiment of 'the invention illustrated in Figure 2 shows the application of the principlesthereofto a'system wherein'a large number of stations may be associated to a central oflice including a switch board circuit, in a similar manner as it is made in telephone systems. Figure 2 shows the coordination 'of circuits and apparatus needed for such a P. B. X "system, having been omitted therein those elements and connections 'which'are not required for the understanding of the operation and "construction. The. element denominated in Figure 2 as IDI, I02, I20, etc., correspond to those denominated I,2, 2|], etc., in'Figure 1.

In Figure 2, only two remote stations IIJI and I02 are shown; their'communication channels MI and I42 respectively lead to the central-office'and are connected 'thereat to the line jacks 43a and 43h respectively. 'Only 8 line .jacks 43a to 43h are shown forming part of the-switch board circuit to be described later on. Three communication control units 5a to I lie located at the central oflice 'are shown in Figure 2. The communication control unitsll l5b and I I5'careidentical "to that demonstrated in Figure 1, whereas the control unit |5a has been adapted in order to serve for lwhat may :be called the operators set. This unit a is cornbinedwith a speaker unit '44 which is "connected directly to the inlet transformer I24 as-it is shown i'n Figure '2. The only circuit modifications provided consist an the following: First, conductor I26, outgoing frnm one terminal of electroma'gnetic device 11 8, is connected to the common conductor 1:3 3 :including a :normally "open switch '45, :and "second, the centertap of the line .ide windin'gqi'f outlet 'tr ans-' former :is not used, owing to the ract that a signal device for the operators set gametessary; The twocommunication control units 1 15b and :IISc'as well as the ioperators set are comple'ted by f cords '46, 41,38, 49 and '50 at the ends of whichplugs 5|, 52, 53 vareiprovided #(the plugs of cords 48 and of control unit =I'I5c areinot shown). Referring :to the switch board Lcircuit, line jack 43a has its inner "contacts connected in series with line-lamp :54 and battery E55; the battery beinggrounded. All the other line .rjacks and line lamps are connected i'na" similar'manner.

To explain the operation -of this system it liS supposed that the party at station 'IIU-I desires to call rstation I02. To attract the attention of :the operator, switch I01 must be closed. Due to "this fact the line lamp 540,, pertaining to line jack 43a, lights on. The operatorvanswers thiss'ignal'by.

i that Changes, therefore, in construction and arrangement may be made without departing from the 2,387,443, inserting plug'53 of cord so into the line jack 43a of the calling party. The inserting of this plug does two things: first,fthe contacts will be ,spread apart disconnecting the linelamp circuit;

allowing the line lamp to extinguish. Second, the opera tor s set becomes conditioned to communicate-with the calling station, the-operator isthus enabled totransmitto and tolisten from station lfll by respectively closing and releasing tions IBIand I92. The plugs l and 52 pertain to 1 communication control unit 5b which for this example was supposed to be unbusy. It will be understood that by inserting the plugs into the 'ja'cks their respective line lamps are disconnected-p In the circuit shown in Figure 2 cords 46 and lead to the inlet and outlet transformers respectivelyof unit 5b and accordingly to the explanation given by description of Figure 1,

- station l lll becomes enabled to control the communication whereas station Hi2 may complete thefsignal circuit. Being so the party Hll operates switch I01, closing it for and keeping it closedfduring the period of transmitting. The

party'at station I02 does not make any manipulation until the moment the conversation has finished. In order to advise the operator at the centraloflice to clear the connections, the party at station I02 c1oses,switohl08 for a moment, thereby completing the signal circuit which results inthat indicator lamp I|9b provided at communication controlunit ll5b lights on.

7 By means provided in combination with the cord circuitbut not shown in Figure 2, lamp l l9b extinguishes when the operator removes the plugs from the jacks, thus clearing the connections of the communication channels MI and The communication control unit itself becomes readyto serve for other communications.

, If there are, say 60 stations in a network, generally 6 or 8 communication control units are suf- -ficient toattain the desired communications according to the average of the daily conversations.

While I have shown and described certain embodiments of my invention, it is to be understood it is capable of many modifications.

spirit and scope of the invention as disclosed in the appended claims, in which it is my intention to claim all novelty inherent in the invention as broadly as permissible, in view of the prior art. What I claim as new and desire to secure by Letters Patent of the United States is:

1. An intercommunication system comprising a central oflice; a plurality of remotely located stations; communication channels between the stations and the central ofifice; a group of communication control units located thereat; each communication control unit having inlet and outlet terminals adapted to be connected to any two of said remotely located stations through their respective communication channels for establishing a communication circuit between said two stations, each communication control unit including in combination, an amplifier, an electromagnetic device responsive to control current, a

reversing switch forming part of the communication; circuit for controlling the direction of the communication being operatively associated with and having its position controlled by said electromagnetic device, means including said electromagnetic device and said inlet terminals providing a normally open control circuit extending through that of the two communication channels which has been connected to said inlet terminals; each of said stations having a speaker unit adapted to function as microphone and means including a normally open switch permitting the electric center point of the communication channelto be grounded; the communication circuit established between two of said stations by insorting a communication control unit at the central oiiice being characterized by the fact that said control circuit may be completed and the direction of communication thereby reversed upon closingof saidswitch belonging to that of the two stations which has been connected to said inlet terminals of said communication control unit at the central oflice. l

-2. An intercommunication system comprising a central ofiice; a plurality of remotely located stations; communication channels between the stations and the central office; a group of communication control units located thereat; eachcommunication control unit having inlet and outlet terminals adapted to beconnected to any two of said remotely located stations through their respective communication channels for establish ing a communication circuit between said two stations, each communication control unit including in combination, an amplifier, an indicator device responsive to signal current, an electromag netic deviceresponsive to control current, a reversing switch forming part of the communication circuit for controlling, the direction of the communication being operatively associated with and having its position controlled by said electromagnetic device, means including said electromagnetic device and said inlet terminals providing a normally open control circuit extending through that of the two communication channels which has been connected to said inlet terminals and means including said indicator device and said outlet terminals providing a normally open signal circuit extending through the other channel which has been connected to said outlet terminals; each of said station having a speaker unit adapted to function as microphone and means including a normally open switch permitting the electric center point of the communication channel to be grounded; the communication circuit established between two of said stations by inserting a communication control unit at the central oflice being characterized by the fact that said control circuit may be completed and the direction of communication thereby reversed upon closing of said switch belonging to that of the two stations which has beenconnected to said inlet terminals whereas said signal circuit may be completed and a signal given to the communication control unit upon closing of said switch belonging to the other station which has been connected to said outlet terminals of said communication control unit at the central oifice.

3. A communication control unit for use in an intercommunicating system of the loudspeaking type wherein speaker units at remote stations are adapted to function as microphones, including in combination, inlet and outlet terminals adapted to be connected to communication channels outgoing from remote stations, two

transformers, "each having its centertapped secondary winding directly connected to said inlet and outlet terminals respectively, an amplifier, an electromagnetic device responsive .to control current, areversing switch operativelyassociated with-and having its position controlledby said electromagnetic device, a common aconductor leading 'to'one of "theterminals of the input and output of said amplifieras well as to one vof the ends of the primary windings of said inlet and outlet transformers, the other ends of the.primary windings of said transformers as well as the other terminalsnof theinpu't and output being-co'nnected to the terminals of said reversing switch in sucha way that'the output'leads to the inlet transformer and the input to the outlet transformer when the reversing switch is i in' its normal position, single terminal connected to said common conductor ..-permitting the control unit "to be grounded, an indicator device responsive to signal current, a source of voltage, a normally open control circuit including said electromagnetic device and said source between said common-conductor and-the centertapof said inlet transformer, and a normally open signal circuit including said indicator device and said source between said common conductor and the centertap of said outlet transformer; being both the control and signal circuits completed by suitable means provided at each station,*whereby respectively the direction of the communication becomes'reversed and a signal is emitted to "said communication control unit.

'4. In an intercommunication system, the combinationincluding, at least two remotely located loudspeakers; a two-wire communicationchannel extending from one'loudspeaker to the other; a communication control unit having inlet and outlet terminals inserted into said communication channel at an intermediate point thereon; said communication control unit including in combination, an amplifier, an indicator device, means including a reversing switch for reversing the-input and output connections of said amplifier with respect to said loudspeakers, a'normally open signal circuit including said indicator -deassvgaca vice andsaid outlet terminals extending through that part of the communication channel which is in connection with :'said outlet terminals -an electro-magnetic 1 device :operati-vely associated withand to fc ontrohtherposition ofsaid reversing,

switch, a normally opencontrol circuit including said electroemagnetic device'andsaid inlet terminals extending through :the =other :part =of-the communication channel outgoing from said inlet terminals; means located at each loudspeaker and operatively associated therewith including a normally-open switch for completingselectively said control circuit -or saidisignal circuit accordin'gl-y to the connection of the loudspeaker "with respectively :said inlet and -outlet terminals o! said communication control unit.

5. Inan intercommunicationsystem, the combination -:including, :at leastit'wo remotely located loudspeakers; a two-wire communication-channal -extending -from one loudspeaker to the other; a communieation control unit having inlet and outlet terminals inserted into said communicamagnetic -device and said inlet terminals :at "said communication control unit and meansincluding-a normally-openswitchprovided at eachloudspeakerfor conditioning that part of the -com munication channel which is connected to -said inlet-terminals to carry on simultaneously both sound and control currents; means including said indicator device and said outlet terminalsat-said communication control unit to cooperate with said mentioned means at the loudspeaker for conditioning the-other part of the communication channel which is outgoing from said outlet terminals to carry on simultaneously both sound and signal currents.

WER- NER HASE'NTBERG. 

